Quantitation of CD4+ lymphocyte levels by flow cytometry is the most common measure of progression of HIV-infected individuals toward frank AIDS. We propose coupling Zynaxix' novel lipophilic cell linkers with existing magnetic bead-based cell separation techniques to produce an inexpensive alternative suitable for routine CD4+ lymphocyte monitoring, allowing FCM resources to be directed towards other tests requiring more operator expertise. Preliminary studies, using fresh mononuclear cell preparations from normal individuals, show high correlation between the Zynaxis assay and flow cytometry. Phase I goals are directed toward assay simplification and validation essential to development of a clinically useful in vitro diagnostic test. Goals include 1) discrimination between CD4+ lymphocytes and monocytes, 2) simplification of specimen preparation, 3) reduction of HIV-related biohazards, and 4) evaluation of the resulting assay in peripheral blood samples having a wide range of CD4+ lymphocyte levels from individuals at different stages of HIV infection. A medical technologist should be able to implement the final procedure in 1-2 days, making it suitable for community hospitals, large clinics, and third world settings.